Substrate plating apparatus

ABSTRACT

A substrate plating apparatus forms an interconnection layer on an interconnection region composed of a fine groove and/or a fine hole defined in a substrate. The substrate plating apparatus includes a plating unit for forming a plated layer on a surface of the substrate including the interconnection region, a chemical mechanical polishing unit for chemically mechanically polishing the substrate to remove the plated layer from the surface of the substrate leaving a portion of the plated layer in the interconnection region, a cleaning unit for cleaning the substrate after the plated layer is formed or the substrate is chemically mechanically polished, a drying unit for drying the substrate after the substrate is cleaned, and a substrate transfer unit for transferring the substrate to and from each of the first plating unit, the first chemical mechanical polishing unit, the cleaning unit, and the drying unit. The first plating unit, the first chemical mechanical polishing unit, the cleaning unit, the drying unit, and the substrate transfer unit are combined into a unitary arrangement.

This application is a divisional of U.S. patent application Ser. No.09/154,895, filed Sep. 17, 1998, and now U.S. Pat. No. 6,294,059.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate plating apparatus forplating a substrate, and more particularly to a substrate platingapparatus for forming a metal interconnection layer in aninterconnection region composed of a fine groove and/or a fine holedefined in a substrate such as a semiconductor wafer or the like.

2. Description of the Related Art

For forming an interconnection circuit on a semiconductor substrate, ithas been customary to deposit a conductive film on a surface of thesemiconductor substrate by sputtering or the like, and remove unwantedareas of the conductive film by chemical dry etching using a patternmask such as a resist or the like.

The material of the interconnection circuit has generally been aluminum(Al) or aluminum alloy. Highly integrated semiconductor circuits havethinner interconnections, which result in increased current densitiesthat are responsible for increased thermal stresses and temperaturerises. As aluminum films become thinner due to stress migration orelectromigration, these problems manifest themselves to the point whereinterconnections tend to be broken down or short-circuited.

Thus, there is a greater demand for using conductive materials such ascopper (Cu) for forming these interconnections, in order to realizelower conductivity and to avoid electromigrations due to currentsflowing therethrough. However, since it is difficult to remove copper orits alloy by dry etching, the conventional process of depositing acopper film and then patterning the copper film by dry etching cannot berelied upon for producing interconnections on substrates. One solutionis to form a desired pattern of interconnection grooves in a substratesurface, and then fill the interconnection grooves with copper or itsalloy. This process does not require any etching process to removeunwanted copper or its alloy. Instead, surface irregularities or stepsare removed from the substrate surface by a polishing process. Theprocess is also advantageous in that interconnection holes forinterconnecting vertical circuit layers can also be formedsimultaneously.

However, as the width of interconnections becomes thinner, thoseinterconnection grooves or holes have a higher aspect ratio, i.e., ahigher ratio of their depth to their diameter or width, and cannotuniformly be filled with copper or its alloy by performing a sputteringoperation.

Chemical vapor deposition (CVD) is widely used for forming films ofvarious materials. Nevertheless, the application of CVD to for theformation of films of copper or its alloy is not promising because it isdifficult to prepare a suitable gaseous material as a source of copperor its alloy. If an organic material is used, carbon (C) tends to beintroduced from the organic material into a deposited film, resulting ingreater electrical resistivity.

There has been proposed a plating process for depositing a copper filmon a substrate. According to the proposed plating process, a substrateis immersed in a plating solution to plate the substrate with copper,i.e. an electroless plating or electroplating procedure, and thenunwanted areas of the plated copper layer is removed by chemicalmechanical polishing (CMP). The plating process makes it possible tofill interconnection grooves of high aspect ratios uniformly with ahighly conductive copper metal. When the plating process is continuouslycarried out within a clean atmosphere in a semiconductor fabricationfacility, however, chemicals or solutions used in a pretreatment processand the plating process are spread as a chemical mist or gas, whichtends to be attached to clean substrates that have been processed in thesemiconductor fabrication facility. This problem arises even if thepretreatment process and the plating process are performed in a sealedprocessing chamber. Specifically, since the sealed processing chamberhas to be opened for loading and unloading substrates, the chemical mistor gas generated in the plating bath or pretreatment bath or chambercannot be prevented from spreading into the semiconductor fabricationfacility.

It has been desired to develop a single apparatus or chamber for forminga plated copper layer on a surface of a semiconductor wafer includinginterconnection regions, which are composed of fine grooves and fineholes, by performing an electroless plating or electroplating operation,and then removing unwanted copper layer portions by performing achemical mechanical polishing operation, thereby leaving the platedcopper layer only in the interconnection regions. However, such a singleapparatus or chamber has not been put to practical use.

If a substrate plating apparatus and a chemical mechanical polishingapparatus are separate from each other, then a semiconductor waferplated with a copper layer has to be dried and unloaded from thesubstrate plating apparatus, and then a dried semiconductor wafer isloaded into the chemical mechanical polishing apparatus for removingunwanted copper portions. Therefore, two separate drying apparatuses orchambers are necessary. In some applications, a protective plated layeris deposited on a plated copper interconnection layer for protecting itssurface. However, since the substrate plating apparatus is separate fromthe chemical mechanical polishing apparatus, the surface of theprotective plated layer tends to be oxidized during the wafer transferfrom the substrate plating apparatus to the chemical mechanicalpolishing apparatus.

The substrate plating apparatus generally comprises a loading andunloading area for transferring cassettes, which store substrates, aplating area for plating substrates, and a cleaning and drying area forcleaning and drying plated substrates. If the substrate platingapparatus, i.e., a wet processing bath which is accommodated in achamber, is placed in a clean room for semiconductor fabricationfacilities, then it is necessary to prevent particles, mists and gassesgenerated from a plating solution or a cleaning solution from beingapplied to semiconductor wafers which have already been processed anddried. Stated otherwise, when processed semiconductor wafers areunloaded from the substrate plating apparatus and transferred to a nextprocessing stage, the particles, mists and gasses from the platingsolution or the cleaning solution should not be spread into the cleanroom, where other manufacturing processes are carried out.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide asubstrate plating apparatus which is free of the various conventionalproblems even when placed in a clean room accommodating semiconductorfabrication facilities. A second object of the present invention is toprovide a substrate plating apparatus which is capable of performing,with a unitary arrangement, various processing operations includingforming a plated layer on a surface of a substrate includinginterconnection regions composed of fine interconnection grooves andfine interconnection holes, and removing unwanted layer portions fromthe substrate, thereby leaving the plated layer in the interconnectionregions as an interconnection layer on the substrate.

Another object of the present invention is to provide a substrateplating apparatus which is effective to prevent particles, mists andgasses of a plating solution and a cleaning solution from spreading intoa clean room as plated semiconductor wafers are transferred in the cleanroom from the plating apparatus to further processing equipment. Theseparticles, mists and gasses are also prevented from spreading.

According to the present invention, there is provided a substrateplating apparatus for forming an interconnection layer on aninterconnection region composed of a fine groove and/or a fine holedefined in a substrate, comprising: a first plating unit for forming alayer on a surface of the substrate including the interconnectionregion; a first chemical mechanical polishing unit for chemicallymechanically polishing the substrate to remove unwanted portions of thelayer from the surface of the substrate; a cleaning unit for cleaningthe substrate after the layer has been formed or after the substrate hasbeen chemically mechanically polished; a drying unit for drying thesubstrate after the substrate has been cleaned; and a substrate transferdevice for transferring the substrate to and from each of the firstplating unit, the first chemical mechanical polishing unit, the cleaningunit, and the drying unit, wherein the first plating unit, the firstchemical mechanical polishing unit, the cleaning unit, the drying unit,and the substrate transfer devices are combined into a unitaryarrangement.

The substrate plating apparatus may further comprise a second platingunit for forming a protective layer over the first layer in theinterconnection region after the unwanted portions have been removed bychemical mechanical polishing from the surface of the substrate, whereinthe second plating unit is part of the unitary arrangement.

The substrate plating apparatus may further comprise a second chemicalmechanical polishing unit for chemically mechanically polishing thesubstrate to remove unwanted portions of the protective layer formedover the first layer in the interconnection region, wherein the secondchemical mechanical polishing unit is part of the unitary arrangement.

The substrate plating apparatus may further comprise a dischargingfacility for discharging a cleaning solution used by the cleaning unitto clean the substrate, wherein the discharging facility is part of theunitary arrangement.

The substrate transfer device may comprise a robot having an arm, withthe first plating unit, the first chemical mechanical polishing unit,the cleaning unit, and the drying unit being accessible to the arm.

The substrate plating apparatus may further comprise concentrationanalyzing devices for analyzing the concentrations of components of aplating solution used by the first plating unit to form the first layer,and plating solution preparing devices for preparing a plating solutionbased on the analyzed concentrations, wherein the concentrationanalyzing devices and the plating solution preparing devices are part ofthe unitary arrangement.

Since at least the first plating unit, the first chemical mechanicalpolishing unit, the cleaning unit, the drying unit, and the substratetransfer device are combined into a unitary arrangement, the substrateplating apparatus offers the following advantages:

1. The steps of forming a first layer on a surface of a semiconductorsubstrate which includes an interconnection region composed of a finegroove and a fine hole, and removing unwanted portions of the firstlayer from the surface of the semiconductor substrate, can be carriedout without multiple drying steps by the substrate plating apparatus

If the first plating unit and the chemical mechanical polishing unitwere independent of each other, a plurality of different drying unitswould be required to dry substrates in association with these units. Thesubstrate plating apparatus of the unitary arrangement does not needsuch different drying units.

2. Down time can be shortened. For example, a substrate can bechemically mechanically polished immediately after plating by a platingsolution bath. Consequently, a first layer is prevented from beingnaturally oxidized, and particles are prevented from being excessivelyapplied to the first layer between such plating and polishing steps.

There is also provided a substrate plating apparatus for plating asubstrate comprising: a loading and unloading area for transferring acassette which stores a substrate; a plating area for plating asubstrate; and a cleaning and drying area for cleaning and drying aplated substrate; wherein the cleaning and drying area is disposedbetween the loading and unloading area and the plating area, a firstpartition is disposed between the loading and unloading area and thecleaning and drying area and has a passage defined therein fortransferring a substrate between the loading and unloading area and thecleaning and drying area, and a second partition is disposed between thecleaning and drying area and the plating area and has a passage definedtherein for transferring a substrate between the cleaning and dryingarea and the plating area.

The substrate plating apparatus may further comprise a first shuttermovably mounted for opening and closing the passage defined in the firstpartition, and a second shutter movably mounted for opening and closingthe passage defined in the second partition.

As described above, the cleaning and drying area is disposed between theloading and unloading area and the plating area. The first partition isdisposed between the loading and unloading area and the cleaning anddrying area, and the second partition is disposed between the cleaningand drying area and the plating area. Therefore, a substrate loaded in adry state is plated and cleaned in the substrate plating apparatus andthe substrate cleaning apparatus, and unloaded in a dry state from thesubstrate plating apparatus. Consequently, even if the substrate platingapparatus is installed in a clean room, the clean room is prevented frombeing contaminated with particles and mists from the plating apparatusand the cleaning apparatus.

When the substrate plating apparatus is installed in a clean room,pressures in the loading and unloading area, the plating area, and thecleaning and drying area are selected such that the pressure in theloading and unloading area is higher than the pressure in the cleaningand drying area, which in turn is higher than the pressure in theplating area, and wherein the pressure in the loading and unloading areais lower than a pressure in the clean room.

Because the pressure in the loading and unloading area is higher thanthe pressure in the cleaning and drying area, which in turn is higherthan the pressure in the plating area, and because the pressure in theloading and unloading area is lower than the pressure in the clean room,air flows in the substrate plating apparatus are prevented from leakinginto the clean room, and hence from contaminating the clean room.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a firstembodiment of the present invention;

FIGS. 2A and 2B are fragmentary cross-sectional views illustrative of aninterconnection plating process carried out by the substrate platingapparatus shown in FIG. 1;

FIG. 3 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a secondembodiment of the present invention;

FIGS. 4A through 4D are fragmentary cross-sectional views illustrativeof an interconnection plating process carried out by the substrateplating apparatus shown in FIG. 3;

FIG. 5 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a thirdembodiment of the present invention;

FIG. 6 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a fourthembodiment of the present invention;

FIG. 7 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a fifthembodiment of the present invention;

FIG. 8 is a schematic view showing airflow in the substrate platingapparatus shown in FIG. 7;

FIG. 9 is a cross-sectional view showing airflows among areas in thesubstrate plating apparatus shown in FIG. 7;

FIG. 10 is a perspective view of the substrate plating apparatus shownin FIG. 7, which is placed in a clean room;

FIG. 11 is a plan view of a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a sixthembodiment of the present invention;

FIG. 12 is a cross-sectional view taken along line XII—XII of FIG. 11;

FIG. 13 is a plan view of a loading stage and a roughly cleaning chamberof the substrate plating apparatus shown in FIG. 11;

FIG. 14 is a cross-sectional view taken along line XIV—XIV of FIG. 13;and

FIG. 15 is a cross-sectional view taken along line XV—XV of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a firstembodiment of the present invention generally comprises a loading unit 1for loading a semiconductor wafer, a copper plating chamber 2 forplating a semiconductor wafer with copper, a pair of water cleaningchambers 3, 4 for cleaning a semiconductor wafer with water, a chemicalmechanical polishing unit 5 for chemically and mechanically polishing asemiconductor wafer, a pair of water cleaning chambers 6, 7 for cleaninga semiconductor wafer with water, a drying chamber 8 for drying asemiconductor wafer, and an unloading unit 9 for unloading asemiconductor wafer with an interconnection layer thereon. The substrateplating apparatus also has a wafer transfer mechanism (not shown) fortransferring semiconductor wafers to the chambers 2, 3, 4, the chemicalmechanical polishing unit 5, the chambers 6, 7, 8, and the unloadingunit 9. The loading unit 1, the chambers 2, 3, 4, the chemicalmechanical polishing unit 5, the chambers 6, 7, 8, and the unloadingunit 9 are combined into a unitary arrangement.

The substrate plating apparatus operates as follows: The wafer transfermechanism transfers a semiconductor wafer W, on which an interconnectionlayer has not yet been formed, from a wafer cassette 1-1 placed in theloading unit 1 to the copper plating chamber 2. In the copper platingchamber 2, as shown in FIG. 2A, a copper layer 103 is formed on asurface of the semiconductor wafer W having an interconnection regioncomposed of an interconnection groove 101 and an interconnection hole(contact hole) 102.

After the copper layer 103 is formed on the semiconductor wafer W in thecopper plating chamber 2, the semiconductor wafer W is transferred tothe water cleaning chambers 3, 4 by the wafer transfer mechanism, andcleaned by water in the water cleaning chambers 3, 4. The cleanedsemiconductor wafer W is transferred to the chemical mechanicalpolishing unit 5 by the wafer transfer mechanism. As shown in FIG. 2B,the chemical mechanical polishing unit 5 removes unwanted portions ofthe copper layer 103 from the surface of the semiconductor wafer W,thereby leaving a portion of the plated copper layer 103 in theinterconnection groove 101 and the interconnection hole 102. In FIGS. 2Aand 2B, a barrier layer 104 made of tin or the like is formed on thesurface of the semiconductor wafer W, including the inner surfaces ofthe interconnection groove 101 and the interconnection hole 102, beforethe copper layer 103 is deposited.

Then, the semiconductor wafer W with the remaining copper layer 103 istransferred to the water cleaning chambers 6, 7 by the wafer transfermechanism, and cleaned by water in the water cleaning chambers 6, 7. Thecleaned semiconductor wafer W is then dried in the drying chamber 8,after which the dried semiconductor wafer W with the remaining copperlayer 103, serving as an interconnection layer, is placed into a wafer,cassette 9-1 in the unloading unit 9.

FIG. 3 shows in plan a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a secondembodiment of the present invention. The substrate plating apparatusshown in FIG. 3 differs from the substrate plating apparatus shown inFIG. 1 in that it additionally includes a copper plating chamber 2′, awater cleaning chamber 10, a pretreatment chamber 11, and a protectivelayer plating chamber 12 for forming a protective layer on a copperlayer on a semiconductor wafer. The loading unit 1, the chambers 2, 2′,3, 4, the chemical mechanical polishing unit 5, the chambers 6, 7, 8,10, 11, 12, and the unloading unit 9 are combined into a unitaryarrangement. Those parts shown in FIGS. 3 and 4A through 4D which areidentical to those shown in FIGS. 1 and 2A, 2B are denoted by identicalreference numerals, and will not be described in detail below.

The substrate plating apparatus shown in FIG. 3 operates as follows: Asemiconductor wafer W is supplied from the wafer cassette 1-1, placed inthe loading unit 1, successively to the copper plating chambers 2, 2′.In the copper plating chamber 2, 2′, as shown in FIG. 4A, a copper layer103 is formed on a surface of a semiconductor wafer W having aninterconnection region composed of an interconnection groove 101 and aninterconnection hole (contact hole) 102. The two copper plating chambers2-, 2′ are employed to allow the semiconductor wafer W to be plated witha copper layer for a long period of time. Specifically, thesemiconductor wafer W may be plated with a primary copper layer byelectroplating in the copper plating chamber 2, and then plated with asecondary copper layer by electroless plating in the copper platingchamber 2′. The substrate plating apparatus may have more than twocopper plating chambers.

The semiconductor wafer W with the copper layer 103 formed thereon iscleaned by water in the water cleaning chambers 3, 4. Then, as shown inFIG. 4B, the chemical mechanical polishing unit 5 removes unwantedportions of the copper layer 103 from the surface of the semiconductorwafer W, thereby leaving a portion of the copper layer 103 in theinterconnection groove 101 and the interconnection hole 102.

Thereafter, the semiconductor wafer W with the remaining copper layer103 is transferred to the water cleaning chamber 10, in which thesemiconductor wafer W is cleaned with water. Then, the semiconductorwafer W is transferred to the pretreatment chamber 11, and pretreatedtherein for the deposition of a protective layer. The pretreatedsemiconductor wafer W is transferred to the protective layer-platingchamber 12. In the protective layer plating chamber 12, as shown in FIG.4C, a protective layer 105 is formed on the copper layer 103 in theinterconnection region on the semiconductor wafer W. For example, theprotective layer 105 is formed with an alloy of nickel (Ni) and boron(B) by electroless plating. After the protective layer 105 is deposited,the semiconductor wafer W is cleaned by water in the water cleaningchambers 6, 7, dried in the drying chamber 8, and then transferred tothe wafer cassette 9-1 in the unloading unit 9.

FIG. 5 shows in plan a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a thirdembodiment of the present invention. The substrate plating apparatusshown in FIG. 5 differs from the substrate plating apparatus shown inFIG. 3 in that it additionally includes a chemical mechanical polishingunit 15, and water cleaning chambers 13, 14. The loading unit 1, thechambers 2, 2′, 3, 4, 14, the chemical mechanical polishing unit 5, 15,the chambers 6, 7, 8, 10, 11, 12, 13, and the unloading unit 9 arecombined into a unitary arrangement. Those parts shown in FIG. 5 whichare identical to those shown in FIG. 3 are denoted by identicalreference numerals, and will not be described in detail below.

In the chemical mechanical polishing unit 15, an upper portion of theprotective layer 105 deposited on the copper layer 103 is polished offto planarize the protective layer 105, as shown in FIG. 4D. The watercleaning chambers 13, 14 additionally clean the semiconductor wafer Wwith water.

FIG. 6 shows in plan a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a fourthembodiment of the present invention. As shown in FIG. 6, the substrateplating apparatus includes a robot 16 at its center which has a robotarm 16-1, and also has a copper plating chamber 2, a pair of watercleaning chambers 3, 4 a chemical mechanical polishing unit 5, apretreatment chamber 11, a protective layer plating chamber 12, a dryingchamber 8, and a loading and unloading station 17, which are disposedaround the robot 16 and positioned within the reach of the robot arm16-1. A loading unit 1 for loading semiconductor wafers and an unloadingunit 9 for unloading semiconductor wafers is disposed adjacent to theloading and unloading station 17. The robot 16, the chambers 2, 3, 4,the chemical mechanical polishing unit 5, the chambers 8, 11, 12, theloading and unloading station 17, the loading unit 1, and the unloadingunit 9 are combined into a unitary arrangement

The substrate plating apparatus shown in FIG. 6 operates as follows:

A semiconductor wafer to be plated is transferred from the loading unit1 to the loading and unloading station 17, from which the semiconductorwafer is received by the robot arm 16-1 and transferred thereby to thecopper plating chamber 2. In the copper plating chamber 2, as shown inFIG. 4A, a copper layer 103 is formed on a surface of the semiconductorwafer which has an interconnection region composed of an interconnectiongroove 101 and an interconnection hole 102. The semiconductor wafer withthe copper layer 103 formed thereon is transferred by the robot arm 16-1to the chemical mechanical polishing unit 5. In the chemical mechanicalpolishing unit 5, as shown in FIG. 4B, unwanted portions of the copperlayer 103 are removed from the surface of the semiconductor wafer W,thereby leaving a portion of the copper layer 103 in the interconnectiongroove 101 and the interconnection hole 102.

The semiconductor wafer is then transferred by the robot arm 16-1 to thewater-cleaning chamber 4, in which the semiconductor wafer is cleaned bywater. Thereafter, the semiconductor wafer is transferred by the robotarm 16-1 to the pretreatment chamber 11, in which the semiconductorwafer is pretreated therein for the deposition of a protective layer.The pretreated semiconductor wafer is transferred by the robot arm 16-1to the protective layer plating chamber 12. In the protective layerplating chamber 12, a protective layer 105 is formed on the copper layer103 in the interconnection region on the semiconductor wafer W, as shownin FIG. 4C. The semiconductor wafer with the protective layer 105 formedthereon is transferred by the robot arm 16-1 to the water cleaningchamber 4, in which the semiconductor wafer is cleaned by water. Thecleaned semiconductor wafer is transferred by the robot arm 16-1 to thedrying chamber 8, in which the semiconductor wafer is dried. The driedsemiconductor wafer is transferred by the robot arm 16-1 to the loadingand unloading station 17, from which the plated semiconductor wafer istransferred to the unloading unit 9.

If the copper plating chambers 2, 2′ of the substrate plating apparatusshown in FIGS. 1, 3, 5, 6 are copper electroplating chambers, then thesubstrate plating apparatus may have a copper ion concentrationanalyzer, an oxygen concentration analyzer, a plating additiveconcentration analyzer, and a plating solution preparing unit forpreparing a plating solution based on analyzed results from theanalyzers. These analyzers and the plating solution preparing unit maybe integrally combined with the other components of the substrateplating apparatus into a unitary arrangement. The substrate platingapparatus may have only some of the above analyzers, rather than all ofthem.

If the copper plating chambers 2, 2′ are copper electroless platingchambers, then the substrate plating apparatus may have a copper ionconcentration analyzer, an oxidizing agent concentration analyzer, areducing agent concentration analyzer, and a pH measuring unit, alongwith a plating solution preparing unit for preparing a plating solutionbased on analyzed results from the analyzers and a pH measured by the pHmeasuring unit. These analyzers, the pH-measuring unit, and the platingsolution preparing unit may be integrally combined with the othercomponents of the substrate plating apparatus into a unitaryarrangement. The substrate plating apparatus may have only some of theabove analyzers and the pH measuring unit, rather than all of them.

If the protective layer plating chamber 12 is an Ni—B electrolessplating chamber, then the substrate plating apparatus may have a nickelion concentration analyzer, an oxidizing agent concentration analyzer, areducing agent concentration analyzer, and a pH measuring unit, alongwith a plating solution preparing unit for preparing a plating solutionbased on analyzed results from the analyzers and a pH measured by the pHmeasuring unit. These analyzers, the pH-measuring unit, and the platingsolution preparing unit may be integrally combined with the othercomponents of the substrate plating apparatus into a unitaryarrangement. The substrate plating apparatus may have only some of theabove analyzers and the pH measuring unit, rather than all of them.

The substrate plating apparatus may have an ion-exchange tower for ionrecovery, an activated carbon extraction tower for organic materialrecovery, a scrubber for processing exhaust gasses, and a solidifier forsolidifying and discarding discharged liquids. The towers, the scrubber,and the solidifier may be integrally combined with the other componentsof the substrate plating apparatus into a unitary arrangement.

The numbers of the plating chambers, water cleaning chambers, and thepretreatment chambers in the substrate plating apparatus shown in FIGS.1, 3, 5, 6 are illustrative only, and these chambers are not limited tothe illustrated numbers.

The chemical mechanical polishing unit may be associated with a slurrysupply unit, a discharged liquid processing unit, and aconstant-temperature chamber, which may be integrally combined with thechemical mechanical polishing unit into a unitary arrangement.

If any one of the illustrated substrate plating apparatus is installedin a clean room, then it is necessary that processed and driedsemiconductor wafers be unloaded and transferred to a next processwithout exposure to mists, particles of; the plating solution or thecleaning solution contained in the apparatus. Therefore, particles andmists in a plating area and a cleaning and drying area of the substrateplating apparatus should not be applied to processed and driedsemiconductor wafers that are stored in a cassette placed in anunloading area of the substrate plating apparatus.

FIG. 7 shows in plan a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a fifthembodiment of the present invention. The substrate plating apparatusshown in FIG. 7 generally comprises a loading and unloading area 20 fortransferring wafer cassettes which store semiconductor wafers, a platingarea 30 for plating semiconductor wafers, and a cleaning and drying area40 for cleaning and drying plated semiconductor wafers. The cleaning anddrying area 40 is positioned between the loading and unloading area 20and the plating area 30. A partition 21 is disposed between the loadingand unloading area 20 and the cleaning and drying area 40, and apartition 23 is disposed between the cleaning and drying area 40 and theplating area 30.

The partition 21 has a passage (not shown) defined therein fortransferring semiconductor wafers therethrough between the loading andunloading area 20 and the cleaning and drying area 40, and supports ashutter 22 for opening and closing the passage. The partition 23 has apassage (not shown) defined therein for transferring semiconductorwafers therethrough between the cleaning and drying area 40 and theplating area 30, and supports a shutter 24 for opening and closing thepassage. The cleaning and drying area 40 and the plating area 30 canindependently be supplied with and discharge air.

The substrate plating apparatus shown in FIG. 7 is placed in a cleanroom, which accommodates semiconductor fabrication facilities. Thepressures in the loading and unloading area 20, the plating area 30, andthe cleaning and drying area 40 are selected as follows:

The pressure in the loading and unloading area 20 is greater than thepressure in the cleaning and drying area 40 which in turn is greaterthan the pressure in the plating area 30.

The pressure in the loading and unloading area 20 is lower than thepressure in the clean room. Therefore, air does not flow from theplating area 30 into the cleaning and drying area 40, and air does notflow from the cleaning and drying area 40 into the loading and unloadingarea 20. Furthermore, air does not flow from the loading and unloadingarea 20 into the clean room.

The loading and unloading area 20 houses a loading unit 20 a and anunloading unit 20 b, each accommodating a wafer cassette for storingsemiconductor wafers. The cleaning and drying area 40 houses two watercleaning units 41 for cleaning plated semiconductor wafers with water,and two drying units 42 for drying plated semiconductor wafers. Each ofthe water cleaning units 41 may comprise a pencil-shaped cleaner with asponge layer mounted on a front end thereof, or a roller with a spongelayer mounted on an outer circumferential surf ace thereof. Each of thedrying units 42 may comprise a drier for spinning a semiconductor waferat a high speed to dehydrate and dry it. The cleaning and drying area 40also has a transfer unit (transfer robot) 43 for transferringsemiconductor wafers.

The plating area 30 houses a plurality of pretreatment chambers 31 forpretreating semiconductor wafers prior to being plated, and a pluralityof plating chambers 32 for plating semiconductor wafers with copper.Each of the pretreatment chambers 31 contains a pretreatment solutionbath including sulfuric acid. A semiconductor wafer can be pretreatedwhen it is immersed in the pretreatment solution bath in thepretreatment chamber 31. Each of the plating chambers 32 contains aplating solution bath including copper sulfate. A semiconductor wafercan be plated with copper when it is immersed in the plating solutionbath in the plating chamber 32. The plating area 30 also has a transferunit (transfer robot) for transferring semiconductor wafers.

FIG. 8 shows in side elevation air flows in the substrate platingapparatus. As shown in FIG. 8, fresh air is introduced from the exteriorthrough a duct 46 and forced through high-performance filters 44 by fansfrom a ceiling 40 a into the cleaning and drying area 40 as downwardclean air flows around the water cleaning units 41 and the drying units42. Most of the supplied clean air is returned from a floor 40 b througha circulation duct 45 to the ceiling 40 a, from which the clean air isforced again through the filters 44 by the fans into the cleaning anddrying area 40. Part of the clean air is discharged from the watercleaning units 41 and the drying units 42 through a duct 52 out of thecleaning and drying area 40.

In the plating area 30 which accommodates the pretreatment chambers 31and the plating chambers 32, particles are not allowed to be applied tothe surfaces of semiconductor wafers even though the plating area 30 isa wet zone. To prevent particles from being applied to semiconductorwafers, downward clean air flows around the pretreatment chambers 31 andthe plating chambers 32. Fresh air is introduced from the exteriorthrough a duct 39 and forced through high-performance filters 33 by fansfrom a ceiling 30 a into the plating area 30.

If the entire amount of clean air as downward clean air flows introducedinto the plating area 30 were always supplied from the exterior, then alarge amount of air would be required to be introduced into anddischarged from the plating area 30 at all times. According to thisembodiment, air is discharged from the plating area 30 through a duct 53at a rate sufficient to keep the pressure in the plating area 30 lowerthan the pressure in the cleaning and drying area 40, and most of thedownward clean air introduced into the plating area 30 is circulatedthrough circulation ducts 34, 35. The circulation duct 34 extends fromthe cleaning and drying area 40 and is connected to the filters 33 overthe ceiling 30 a. The circulation duct 35 is disposed in the cleaningand drying area 40 and connected to the pipe 34 in the cleaning anddrying area 40.

The circulating air that has passed around the pretreatment chambers 31and the plating chambers 32 contains a chemical mist and gasses fromsolution bathes. The chemical mist and gasses are removed from thecirculating air by a scrubber 36 and mist separators 37, 38 which aredisposed in the pipe 34 that is connected to the pipe 35. The air whichcirculates from the cleaning and drying area 40 through the scrubber 36and the mist separators 37, 38 back into the circulation duct 34 overthe ceiling 30 a is free of any chemical mist and gasses. The clean airis then forced through the filters 33 by the fans to circulate back intothe plating area 30.

Part of the air is discharged from the plating area 30 through the duct53 connected to a floor 30 b of the plating area 30. Air containing achemical mist and gasses is also discharged from a plating solutioncirculating tank 50 and an H₂SO₄ circulating tank 51 in the plating area30, through the duct 53. An amount of fresh air which is commensuratewith the amount of air discharged through the duct 53 is supplied fromthe duct 39 into the plating chamber 30 under the negative pressuredeveloped therein with respect to the pressure in the clean room.

As described above, the pressure in the loading and unloading area 20 ishigher than the pressure in the cleaning and drying area 40 which ishigher than the pressure in the plating area 30. When the shutters 22,24 (see FIG. 7) are opened, therefore, air flows successively throughthe loading and unloading area 20, the cleaning and drying area 40, andthe plating area 30, as shown in FIG. 9. Air discharged from thecleaning and drying area 40 and the plating area 30 flows through theducts 52, 53 into a common duct 54 (see FIG. 10) which extends out ofthe clean room.

FIG. 10 shows in perspective the substrate plating apparatus shown inFIG. 7, which is placed in the clean room. The loading and unloadingarea 20 includes a side wall which has a cassette transfer port 55defined therein and a control panel 56, and which is exposed to aworking zone 58 that is compartmented in the clean room by a partitionwall 57. The partition wall 57 also compartments a utility zone 59 inthe clean room in which the substrate plating apparatus is installed.Other sidewalls of the substrate plating apparatus are exposed to theutility zone 59 whose air cleanliness is lower than the air cleanlinessin the working zone 58.

As described above, the cleaning and drying area 40 is disposed betweenthe loading and unloading area 20 and the plating area 30. The partition21 is disposed between the loading and unloading area 20 and thecleaning and drying area 40, and the partition 23 is disposed betweenthe cleaning and drying area 40 and the plating area 30. A drysemiconductor wafer is loaded from the working zone 58 through thecassette transfer port 55 into the substrate plating apparatus, and thenplated in the substrate plating apparatus. The plated semiconductorwafer is cleaned and dried, and then unloaded from the substrate platingapparatus through the cassette transfer port 55 into the working zone58. Consequently, no particles and mist are applied to the surface ofthe semiconductor wafer, and the working zone 58 which has higher aircleanliness than the utility zone 57 is prevented from beingcontaminated by particles, chemical mists, and cleaning solution mists.

In the fifth embodiment shown in FIGS. 7 and 8, the substrate platingapparatus has the loading and unloading area 20, the cleaning and dryingarea 40, and the plating area 30. However, an area accommodating achemical mechanical polishing unit may be disposed in or adjacent to theplating area 30, and the cleaning and drying area 40 may be disposed inthe plating area 30 or between the area accommodating the chemicalmechanical polishing unit and the loading and unloading area 20. Any ofvarious other suitable area and unit layouts may be employed insofar asa dry semiconductor wafer can be loaded into the substrate platingapparatus, and a plated semiconductor wafer can be cleaned and dried,and thereafter unloaded from the substrate plating apparatus.

FIGS. 11 through 15 show a substrate plating apparatus for forminginterconnections on a semiconductor wafer according to a sixthembodiment of the present invention.

As shown in FIG. 11, the substrate plating apparatus, generally denotedby 110, has a contaminated zone 112 and a clean zone 113 divided by apartition 111. The contaminated zone 112 and the clean zone 113 canindependently be supplied with and discharge air. The pressure in theclean zone 113 is higher than the pressure in the contaminated zone 112.

The clean zone 113 accommodates a loading unit 114 a, an unloading unit114 b, two water cleaning and drying units 160 for cleaning and dryingplated semiconductor wafers, and a transfer unit (transfer robot) 161for transferring semiconductor wafers. The contaminated zone 112accommodates two pretreatment chambers 118 for pretreating semiconductorwafers by pretreating solution baths, a plurality of plating chambers119 for plating semiconductor wafers with copper by plating solutionbaths, and a transfer unit (transfer robot) 162 for transferringsemiconductor wafers.

The pretreatment chambers 118 and the plating chambers 119 are similarin structure and operation to those according the previous embodiments.

As shown in FIG. 12, the transfer unit 162 disposed in the contaminatedzone 112 comprises a six-axis robot, for example, having a plurality ofinterconnected arms 163 with an openable and closable grip hand 164mounted on a tip end of the arms 163. The grip hand 164 is in the formof a ring having a plurality of rotatable rollers 165 mounted on aninner circumferential surface thereof.

As shown in FIGS. 11 and 13, a loading stage 167 having a plurality(four in the illustrated embodiment) of support bases 166 is mounted inthe clean zone 113 adjacent to the partition 111. The transfer unit 161in the clean zone 113 holds a semiconductor wafer W to be plated andplaces the semiconductor wafer W onto the support bases 166 of theloading stage 167, and then the transfer unit 162 in the contaminatedzone 112 picks up the semiconductor wafer W from the support bases 166.

As shown in FIG. 13, a partition wall 170 is disposed between theloading stage 167 and the partition 111. The partition wall 170 has anopening 170 a defined therein for passage of the grip hand 164 of thetransfer unit 162 therethrough and a shutter 172 actuatable by acylinder 171 for opening and closing the opening 170 a. The partition111 also has an opening 111 a defined therein for passage of the griphand 164 of the transfer unit 162 therethrough.

A roughly cleaning chamber 183 is positioned adjacent to the partition111 in juxtaposed relation to the loading stage 167. The roughlycleaning chamber 183 is defined as a box by a rear partition wall 180contiguous to the partition wall 170, a front partition wall 181 of asubstantially C-shape joined to the rear partition wall 180, and aceiling 182 (see FIG. 15). The roughly cleaning chamber 183 accommodatesan unloading stage 185 having a plurality of (four in the illustratedembodiment) support bases 184. The unloading stage 185 is identical instructure to the loading stage 167.

As shown in FIG. 15, two vertically spaced arrays of ejection nozzles186 for ejecting a cleaning solution are disposed in the roughlycleaning chamber 183.

As shown in FIGS. 13 and 15, the rear partition wall 180 has an opening180 a defined therein for passage of the grip hand 164 of the transferunit 162 in the contaminated zone 112 therethrough and a shutter 188actuatable by a cylinder 187 for opening and closing the opening 180 a.The front partition wall 181 has an opening 181 a defined therein forpassage of a grip hand of the transfer unit 161 in the clean zone 113therethrough and a shutter 190 actuatable by a cylinder 189 for openingand closing the opening 181 a. The opening 111 a in the partition 111extends from a position behind the loading stage 167 all the way to aposition behind the roughly cleaning chamber 183 for allowing the griphand 164 of the transfer unit 162 to move freely toward and away fromthe openings 170 a, 180 a.

As shown in FIG. 14, the shutter 188 has a recess 188 a defined in anupper edge thereof for passage therethrough of only the arms 163 of thetransfer unit 162.

The grip hand 164 of the transfer unit 162 in the contaminated zone 112can be inserted through the recess 188 a into the roughly cleaningchamber 183. Therefore, the grip hand 164 and a plated semiconductorwafer W gripped thereby can be roughly cleaned in the roughly cleaningchamber 183. After the grip hand 164 and the plated semiconductor waferW gripped thereby are roughly cleaned, the grip hand 164 places thesemiconductor wafer W onto the support bases 184 of the unloading stage185. The semiconductor wafer W placed on the support bases 184 isroughly cleaned again, and thereafter picked up by the transfer unit 161in the clean zone 113.

More specifically, the shutter 188 is opened by being lowered by thecylinder 187, and a plated semiconductor wafer W gripped by the griphand 164 of the transfer unit 162 is introduced into the roughlycleaning chamber 183. The shutter 188 is then lifted, and with the arms163 of the transfer unit 162 being inserted through the recess 188 a,the ejection nozzles 186 eject a cleaning solution to the semiconductorwafer W for thereby roughly cleaning the grip hand 164 and thesemiconductor wafer W. Thereafter, the roughly cleaned semiconductorwafer W is placed onto the support bases 184, and the grip hand 164 isretracted out of the roughly cleaning chamber 183. Then, the shutter 188is fully closed.

Then, the ejection nozzles 186 eject a cleaning solution again to thesemiconductor wafer W on the support bases 184 for roughly cleaning thesemiconductor wafer W again. Thereafter, the shutter 190 is opened, andthe grip hand of the transfer unit 161 in the clean zone 113 is insertedinto the roughly cleaning chamber 183. After the grip hand of thetransfer unit 161 picks up the semiconductor wafer W and removes thesemiconductor wafer W from the roughly cleaning chamber 183, the shutter190 is closed.

Because the grip hand 164 of the transfer unit 162 in the contaminatedzone 112 is roughly cleaned together with the plated semiconductor waferW, the plating solution is prevented from being applied to and depositedon the grip hand 164. Consequently, the grip hand 164 does not transferany substantial contamination to the transfer unit 161 in the clean zone113.

In the illustrated sixth embodiment, the clean zone 113 accommodates theloading stage 167 and the roughly cleaning chamber 183, which houses theunloading stage 185. However, the loading stage 167 and the roughlycleaning chamber 183 which houses the unloading stage 185 may bedisposed in the contaminated zone 112.

In the illustrated embodiments, the present invention is applied to thesubstrate plating apparatus for plating a semiconductor wafer. However,the principles of the present invention are also applicable to asubstrate plating apparatus for plating a substrate other than asemiconductor wafer. Furthermore, a region on a substrate plated by thesubstrate plating apparatus is not limited to an interconnection regionon the substrate. The substrate plating apparatus may be used to platesubstrates with a metal other than copper.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1. An apparatus for forming a layer on a substrate, comprising: aloading and unloading area to transfer a substrate; a plating area toform a layer on the substrate; a concentration analyzing device toanalyze concentrations of components of a plating solution used by saidplating area; and a cleaning and drying area to clean and dry thesubstrate.
 2. The apparatus according to claim 1, wherein saidconcentration analyzing device includes at least one of: (i) a copperion concentration analyzer; (ii) an oxidizing agent concentrationanalyzer; (iii) a reducing agent concentration analyzer; (iv) a pHmeasuring unit; (v) an oxygen concentration analyzer; and (vi) a platingadditive concentration analyzer.
 3. The apparatus according to claim 1,further comprising: a plating solution preparing device to prepare aplating solution based on the concentrations analyzed by saidconcentration analyzing device.
 4. The apparatus according to claim 1,wherein said loading and unloading area includes a transfer device totransfer the substrate from said plating area to said loading andunloading area.
 5. The apparatus according to claim 4, wherein saidtransfer device comprises a robot.
 6. The apparatus according to claim4, wherein said transfer device comprises a first transfer unit and asecond transfer unit.
 7. The apparatus according to claim 6, whereinsaid first transfer unit is to transfer the substrate between saidloading and unloading area and said cleaning and drying area and saidsecond transfer unit is to transfer the substrate between said cleaningand drying area and said plating area.
 8. The apparatus according toclaim 1, wherein said plating area includes a transfer device.
 9. Theapparatus according to claim 8, wherein said transfer device comprises arobot.
 10. The apparatus according to claim 1, wherein the first layeris a copper layer.
 11. The apparatus according to claim 1, furthercomprising: airflow ducts for forming airflows in said plating area. 12.The apparatus according to claim 1, wherein said plating area includesat least one pretreatment chamber containing a pretreatment solutionbath and at least one plating chamber containing a plating solutionbath.
 13. The apparatus according to claim 1, wherein said cleaning anddrying area is disposed between said loading and unloading area and saidplating area.
 14. The apparatus according to claim 1, wherein saidplating area includes a plating unit to electrolessly form a copperlayer on the substrate.
 15. The apparatus according to claim 1, whereinsaid cleaning and drying area includes a first cleaning and dryingarrangement and a second cleaning and drying arrangement.
 16. Theapparatus according to claim 15, wherein said apparatus includes agenerally longitudinally extending line passing through said loading andunloading area, said cleaning and drying area and said plating area, andwherein said first and second cleaning and drying arrangements arepositioned on opposite sides of said generally longitudinally extendingline.
 17. The apparatus according to claim 16, wherein said cleaning anddrying area is disposed between said loading and unloading area and saidplating area in a direction of said generally longitudinally extendingline.
 18. A substrate plating apparatus installed in a clean room forplating a semiconductor substrate, comprising: a plating unit comprisingat least one plating chamber for containing a plating solution forplating a metal layer on the semiconductor substrate, wherein airpressure in said plating unit is lower than air pressure in said cleanroom; a concentration analyzing device to analyze concentrations of theplating solution, wherein said concentration analyzing device comprisesa metal ion concentration analyzer and a plating additive concentrationanalyzer; a plating solution preparing unit for preparing the platingsolution based on analyzed results from said concentration analyzingdevice; and a cleaning and drying unit for cleaning and drying theplated semiconductor substrate.
 19. The apparatus according to claim 18,wherein said concentration analyzing device includes at least one of:(i) a copper ion concentration analyzer; (ii) an oxidizing agentconcentration analyzer; (iii) a reducing agent concentration analyzer;(iv) a pH measuring unit; (v) an oxygen concentration analyzer; and (vi)a plating additive concentration analyzer.
 20. The apparatus accordingto claim 18, further comprising: a loading and unloading area includinga transfer device to transfer the substrate from said plating unit tosaid loading and unloading area.
 21. The apparatus according to claim20, wherein said transfer device comprises a robot.
 22. The apparatusaccording to claim 21, wherein said transfer device comprises a firsttransfer unit and a second transfer unit.
 23. The apparatus according toclaim 22, wherein said first transfer unit is to transfer the substratebetween said loading and unloading area and said cleaning and dryingunit and said second transfer unit is to transfer the substrate betweensaid cleaning and drying unit and said plating unit.
 24. The apparatusaccording to claim 18, wherein said plating unit includes a transferdevice.
 25. The apparatus according to claim 24, wherein said transferdevice comprises a robot.
 26. The apparatus according to claim 18,wherein the first layer is a copper layer.
 27. The apparatus accordingto claim 18, further comprising: airflow ducts for forming airflows insaid plating unit.
 28. The apparatus according to claim 18, wherein saidplating unit includes at least one pretreatment chamber containing apretreatment solution bath and at least one plating chamber containing aplating solution bath.
 29. The apparatus according to claim 18, furthercomprising: a loading and unloading area, wherein said cleaning anddrying unit is disposed between said loading and unloading area and saidplating unit.
 30. The apparatus according to claim 18, wherein saidplating unit includes an electroless plating unit to electrolessly forma copper layer on the substrate.
 31. The apparatus according to claim18, wherein said cleaning and drying unit includes a first cleaning anddrying arrangement and a second cleaning and drying arrangement.
 32. Theapparatus according to claim 31, further comprising: a loading andunloading area, wherein said apparatus includes a generallylongitudinally extending line passing through said loading and unloadingarea, said cleaning and drying unit and said plating unit, and whereinsaid first and second cleaning and drying arrangements are positioned onopposite sides of said generally longitudinally extending line.
 33. Theapparatus according to claim 32, wherein said cleaning and drying unitis disposed between said loading and unloading area and said platingunit in a direction of said generally longitudinally extending line. 34.A substrate plating apparatus for plating a semiconductor substrate,comprising: at least one plating chamber for containing a platingsolution for electrolessly plating a metal layer on the semiconductorsubstrate; a concentration analyzing device to analyze concentrations ofthe plating solution, wherein said concentration analyzing devicecomprises a metal ion concentration analyzer, a plating additiveconcentration analyzer, and a pH measuring unit; a plating solutionpreparing unit for preparing the plating solution based on analyzedresults from said concentration analyzing device; and a cleaning anddrying unit for cleaning and drying the plated semiconductor substrate.35. The apparatus according to claim 34, wherein said concentrationanalyzing device includes at least one of: (i) a copper ionconcentration analyzer; (ii) an oxidizing agent concentration analyzer;(iii) a reducing agent concentration analyzer; (iv) a pH measuring unit;(v) an oxygen concentration analyzer; and (vi) a plating additiveconcentration analyzer.
 36. The apparatus according to claim 34, furthercomprising: a loading and unloading area including a transfer device totransfer the substrate from said at least one plating chamber to saidloading and unloading area.
 37. The apparatus according to claim 36,wherein said transfer device comprises a robot.
 38. The apparatusaccording to claim 36, wherein said transfer device comprises a firsttransfer unit and a second transfer unit.
 39. The apparatus according toclaim 38, wherein said first transfer unit is to transfer the substratebetween said loading and unloading area and said cleaning and dryingunit and said second transfer unit is to transfer the substrate betweensaid cleaning and drying unit and said at least one plating chamber. 40.The apparatus according to claim 34, further comprising: a transferdevice associated with said at least one plating chamber.
 41. Theapparatus according to claim 40, wherein said transfer device comprisesa robot.
 42. The apparatus according to claim 34, wherein the firstlayer is a copper layer.
 43. The apparatus according to claim 34,further comprising: airflow ducts for forming airflows in the vicinityof said at least one plating chamber.
 44. The apparatus according toclaim 34, further comprising: at least one pretreatment chambercontaining a pretreatment solution bath.
 45. The apparatus according toclaim 34, further comprising: a loading and unloading area, wherein saidcleaning and drying unit is disposed between said loading and unloadingarea and said at least one plating chamber.
 46. The apparatus accordingto claim 34, further comprising: a plating unit that includes said atleast one plating chamber.
 47. The apparatus according to claim 34,wherein said cleaning and drying unit includes a first cleaning anddrying arrangement and a second cleaning and drying arrangement.
 48. Theapparatus according to claim 47 further comprising: a loading andunloading area; and a plating unit that includes said at least oneplating chamber, wherein said apparatus includes a generallylongitudinally extending line passing through said loading and unloadingarea, said cleaning and drying unit and said plating unit, and whereinsaid first and second cleaning and drying arrangements are positioned onopposite sides of said generally longitudinally extending line.
 49. Theapparatus according to claim 48, wherein said cleaning and drying unitis disposed between said loading and unloading area and said platingunit in a direction of said generally longitudinally extending line.